The West Nile virus

Mother Nature's biological warfare

Getting as far as the White House lawn

AMERICANS had almost forgotten that nature can spread disease as efficiently as any bioterrorist. They remembered, with a gulp, when a recent addition to America's disease lexicon, the West Nile virus, reared its head again in mid-June. About a month ahead of its usual season, West Nile has already caused five deaths in Louisiana and made more than 100 people ill, including quite a few youngsters. This year's outbreak is already the worst since the virus appeared in New York city in 1999.

West Nile virus was first identified in Uganda in 1937, and is endemic in the Middle East, Africa and parts of Europe. It was probably brought to America by an imported bird that had been bitten by mosquitoes, which then infected other animals and people.

The virus does not usually affect humans. Only one in five people who are infected develop symptoms, and only one in 150 of those become severely ill or die from the brain inflammation that is its worst result. Experts say they expected West Nile to spread across the country as it has done, from only a few north-eastern states in 1999 to 34 states and Washington, DC, so far this year. It would take a brisk set of bioterrorists to move germs this efficiently.

Three weeks ago, an infected bird was found as close to power as the White House lawn. It is fortunate, therefore, that the systems set up to manage bioterrorism will also prove useful in handling West Nile. Public health departments and hospitals are now communicating much more often and with better technology than before September 11th and last year's anthrax attacks. Health officials in some cities can now see when emergency rooms are becoming overcrowded. Chicago's hospitals are sharing information on the availability of beds, respirators and other equipment. Medical emergency teams will sometimes also respond to severe disease outbreaks that are not part of a war.

The bioterror systems will be used to monitor the West Nile virus. Most states east of the Mississippi have also been spraying and treating standing water to destroy adult mosquitoes and their larvae. Still, health officials expect many more human cases of the disease as the summer progresses. With luck, its impact will be limited. One survivor said he found his illness easier to cope with than watching his baseball team blow ninth-inning leads.